The formation of helium lines in the Sun is not understood.
There are at least two SOHO scientific investigations addressing this
issue (PI's C. Jordan, S. Jordan). Neither of these proposals
considers explicitly the effects of dynamic evolution of the emitting
plasma. Here we wish to measure He I and He II (Balmer) line
profiles as a function of time using the unique capabilities of
SUMER, coupled with supporting lines formed in the corona and
chromosphere and with imaging data from CDS and EIT.

Why might dynamics be important? First, Fleck and colleagues (1995
Proc. 15th NSO/SP workshop, Ed. Kuhn & Penn) have discovered some
remarkable features of time series data of He I line
and the Ca II K line. The line center and velocities vary
in phase, but the former shows substantially smaller velocity
amplitudes. Carlsson & Stein's (1994 ApJL) radiation hydrodynamic
simulations have shown (also remarkably) that time series Ca II H
profile data in the interiors of supergranule cells are consistent
with a dynamic chromosphere- static models are incapable of capturing
even basic elements of the line formation. Second, Helium
ions have anomalously long recombination (and ionization) times t. For He I
sec, for He II sec, where
is the electron density in units of cm. These are in excess of
known variablity of both chromospheric and coronal dynamcal timescales
even in the quiet Sun (wide slit ``movies'' in Mg IX
368, He I 584 and O V 629 from CDS
graphically illustrate this point). Lastly, dynamical signatures can
reduce dramatically ambiguities in understanding the formation of
spectral features, through phase and amplitude dependencies in
comparison with better understood lines.

Measuring profiles has the added advantage of providing
model-independent information about the thermal properties of the
emitting plasma. For instance Wahlstrom & Carlsson (1994 ApJ 433, 417)
showed from linewidths of He II Ba- from HRTS data that the
plasma emitting this line was at K or less.

We wish to measure line profiles with SUMER at two wavelength
positions measured at the He I resonance line () and at the He II
Ba- line respectively, using 7.5 and 10 second
integration times. We would also measure profiles of lines of neutral
species and of better understood transition region lines. This choice
of lines will allow us to examine time dependence of He I and He II
line profiles relative to lines whose formation is better understood.
Fortuitously, the He II Ba- line can be observed
simultaneously with the (on average weak) transition of He I at 537.03Å.
(Ba- and Ba- of He II are not observable with SUMER.
Higher Lyman lines are weaker and are not observable with He I lines
at the same slit position.)

We wish to observe the quiet Sun in and outside of coronal holes and
at least one active region. This is not only to move between
different spectrum formation regimes in the importance of electron
excitations versus photo-excitations, but also to look for
different dynamical signatures between different solar regions.
Observed profiles will be compared with those from radiation
hydrodynamcal simulations.

Note that the He-II Ba- region of the SUMER predicted spectra
in the red book is incomplete. In the red book there are three
``lines'' between 1082 and 1087Å, N II 1084.58, He II 1084.975, N II
1085.701. The N II lines belong to a multiplet which has 6 lines. The provisional SUMER
quiet Sun atlas shows four features of comparable strength- three N II
features including all 6 lines and the He II Ba- line.
Furthermore the SUMER atlas data almost fully resolved the He II lines
from N II, and show that mean quiet Sun count rates are adequate for our
proposed study.

We will ask for supporting observations with the NIS mode of CDS and
in the Fe IX/X channel of EIT.